{"id":2228333,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2228333/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260426024507.597480-1-marex@nabladev.com/","project":{"id":35,"url":"http://patchwork.ozlabs.org/api/1.1/projects/35/?format=json","name":"Linux I2C development","link_name":"linux-i2c","list_id":"linux-i2c.vger.kernel.org","list_email":"linux-i2c@vger.kernel.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260426024507.597480-1-marex@nabladev.com>","date":"2026-04-26T02:44:32","name":"[v2] nvmem: core: Default to read-only if wp-gpios present","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"ced4e04c017474b265e748a45550b399584793f0","submitter":{"id":91452,"url":"http://patchwork.ozlabs.org/api/1.1/people/91452/?format=json","name":"Marek Vasut","email":"marex@nabladev.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260426024507.597480-1-marex@nabladev.com/mbox/","series":[{"id":501499,"url":"http://patchwork.ozlabs.org/api/1.1/series/501499/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/list/?series=501499","date":"2026-04-26T02:44:32","name":"[v2] nvmem: core: Default to read-only if wp-gpios present","version":2,"mbox":"http://patchwork.ozlabs.org/series/501499/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2228333/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2228333/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-i2c@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=nabladev.com header.i=@nabladev.com header.a=rsa-sha256\n header.s=dkim header.b=gJk3nKDC;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; 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c=relaxed/simple;\n\tbh=P6vg/u8mtaOqDTc++MuUp6HgFqxSPaUF8GiwXM2ZEw0=;\n\th=From:To:Cc:Subject:Date:Message-ID:MIME-Version;\n b=Kvoc7f+4/6CZsTTrtRFNO/75/oIKNR5v0SA2uCpz+8kCbhy++It0hc4tl7FIQFyfkyjQtxDkMeDIr4OCwQSRFMY95EZhVAQLXnXN+iLRxnc/0tj1XCeKS46m7mOl9xXl6vPkdN3gxk063lYB/iFvos9N9x4iosRE0OBUKFwmkSE=","ARC-Authentication-Results":"i=1; smtp.subspace.kernel.org;\n dmarc=pass (p=reject dis=none) header.from=nabladev.com;\n spf=pass smtp.mailfrom=nabladev.com;\n dkim=pass (2048-bit key) header.d=nabladev.com header.i=@nabladev.com\n header.b=gJk3nKDC; arc=none smtp.client-ip=178.251.229.89","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=nabladev.com;\n\ts=dkim; t=1777171515; h=from:subject:date:message-id:to:cc:mime-version:\n\t content-transfer-encoding; bh=OCw1cmmN/s4IqyAwm6S/ENA1IUWW4c1JPYW+MdOnM6w=;\n\tb=gJk3nKDC0OQ5FIOvLERMM5dIY8XkXJSsCGm5gd0ljl36aByaPr4oo0mmHtDs43ym+00OIN\n\tSvqcjo7LF696g3B9CLdQucNrmMtmoT3vxK3h3c2tYQto/ib1muGj5MUM0zjWPFTwn/yhu7\n\t/o6GLXhvHZdLsgdRmy3ZXkgDFTjMPbjExmRDPO0EjxTTc8aYslugZNQieYED8kTLMnD/Ec\n\tJ6LAh3T+cR7TsqMYm3SR6GraNJokNy1Yr0V/NXx3B9BA0VzqpB5WwugEUFQqCLxgQ9f1jT\n\t5FtvRn+GZ7IUMumLrI5kUPU9Jj1G3w5pue4bWWx+ePHp01bFEQoAA+auh1u4dQ==","From":"Marek Vasut ","To":"linux-i2c@vger.kernel.org","Cc":"Marek Vasut ,\n\tArnd Bergmann ,\n\tBartosz Golaszewski ,\n\tGreg Kroah-Hartman ,\n\tSrinivas Kandagatla ,\n\tlinux-kernel@vger.kernel.org","Subject":"[PATCH v2] nvmem: core: Default to read-only if wp-gpios present","Date":"Sun, 26 Apr 2026 04:44:32 +0200","Message-ID":"<20260426024507.597480-1-marex@nabladev.com>","X-Mailer":"git-send-email 2.53.0","Precedence":"bulk","X-Mailing-List":"linux-i2c@vger.kernel.org","List-Id":"","List-Subscribe":"","List-Unsubscribe":"","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-Last-TLS-Session-Version":"TLSv1.3"},"content":"In case the nvmem DT node contains \"wp-gpios\" DT property, the device\ncurrently defaults to read-write and the force_ro sysfs attribute reads\n0. Switch to the default read-only, which is both safer, and aligned\nwith eMMC HW BOOT partition force_ro sysfs attribute behavior, which\nalso defaults to read-only.\n\nThe adjustment of nvmem->read_only value to read-only in case wp-gpios\nDT property is present must be done only after the device_add() got\ncalled because device_add() does internally call nvmem_bin_attr_get_umode(),\nwhich configures the permissions of 'nvmem' bin attr based on the value\nof nvmem->read_only that is only parsed from DT property 'read-only',\nwithout any adjustment. This way, if DT property 'read-only' is present,\nthe 'nvmem' attribute is always read-only. Otherwise, if the device is\nwriteable, then 'nvmem' attribute is writeable, and nvmem->read_only\ndefaults to read-only, but can be switched to read-write at runtime via\nthe 'force_ro' attribute.\n\nThe updated behavior can be tested as follows:\n\nCurrent content:\n\"\n$ cat /sys/bus/nvmem/devices/logging7/force_ro\n1\n\n$ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem\n00000000 66 6f 6f 0a ff ff ff ff\n\"\n\nWrite into default-read-only device:\n\"\n$ echo bar > /sys/bus/nvmem/devices/logging7/nvmem\nbash: echo: write error: Operation not permitted\n$ cat /sys/bus/nvmem/devices/logging7/force_ro\n1\n\"\n\nUnlock and write into device:\n\"\n$ echo 0 > /sys/bus/nvmem/devices/logging7/force_ro\n$ cat /sys/bus/nvmem/devices/logging7/force_ro\n0\n\n$ echo bar > /sys/bus/nvmem/devices/logging7/nvmem\n$ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem\n00000000 62 61 72 0a ff ff ff ff\n\"\n\nRelock and write into device, fails because device is read-only again:\n\"\n$ echo 1 > /sys/bus/nvmem/devices/logging7/force_ro\n$ echo baz > /sys/bus/nvmem/devices/logging7/nvmem\nbash: echo: write error: Operation not permitted\n\n$ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem\n00000000 62 61 72 0a ff ff ff ff\n\"\n\nSigned-off-by: Marek Vasut \n---\nCc: Arnd Bergmann \nCc: Bartosz Golaszewski \nCc: Greg Kroah-Hartman \nCc: Srinivas Kandagatla \nCc: linux-i2c@vger.kernel.org\nCc: linux-kernel@vger.kernel.org\n---\nV2: Simplify the implementation, make devices with wp-gpios default\n to read-only and let users unlock those devices via force_ro\n sysfs attribute, just like eMMC HW BOOT partitions\n---\n drivers/nvmem/core.c | 6 ++++++\n 1 file changed, 6 insertions(+)","diff":"diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c\nindex 311cb2e5a5c02..0b1942e389113 100644\n--- a/drivers/nvmem/core.c\n+++ b/drivers/nvmem/core.c\n@@ -1019,6 +1019,12 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)\n \tif (rval)\n \t\tgoto err_remove_dev;\n \n+\t/* If the device has WP GPIO, default to read-only */\n+\tif (nvmem->wp_gpio) {\n+\t\tnvmem->read_only = true;\n+\t\tgpiod_set_value_cansleep(nvmem->wp_gpio, 1);\n+\t}\n+\n #ifdef CONFIG_NVMEM_SYSFS\n \trval = nvmem_populate_sysfs_cells(nvmem);\n \tif (rval)\n","prefixes":["v2"]}